Table 2 Risk of second fatal malignancy using protons compared to photon treatments

Schneider 2006 [48]

Primary and out-of-field

Proton dose :calculated by TPS (PSI proton treatment planning program)

Organ equivalent doses

SS

Approximately 50% reduction in risk of second cancer with SS protons compared to 15MV 3D-CRT using both LE and LP models

LE

Neutron dose: measured in phantom- previously published data

LP

Schneider 2007 [49]

Primary and out-of field

Proton dose :calculated by TPS (PSI proton treatment planning program)

Organ equivalent dose

SS

Risk from 100Gy protons relative to 70Gy 15MV 3D-CRT:

LNT

− 40.7% (LE)

Neutron dose: measured in phantom- previously published data

LE

− 41.3% (LP)

LP

− 40.0% (LNT)

Fontenot 2009 [36]

Primary and out-of-field

Primary dose: calculated by TPS (Eclipse).

Equivalent doses

PS

Compared to 6MV step and shoot IMRT, ratio of excess relative risk with protons:

Ratio of excess relative risk (RRR)

0.61 (small patient)

Proton scatter: Monte Carlo simulations- previously published

BEIR organ specific risk co-efficients

0.66 (medium patient)

0.74 (large patient)

Photon scatter:

Measured in phantom- previously published data

LNT**

Fontenot 2010 [28]

Primary and out-of-field

Primary dose: calculated by TPS (Eclipse).

As above

PS

Compared to 6MV step and shoot IMRT, ratio of excess relative risk with protons:

Weighting for neutrons also varied

Proton scatter: Monte Carlo simulations- previously published

0.66 (95%CI: 0.63-0.69; neutron weighting 1)

0.61 (95%CI: 0.59-0.63; neutron weighting 0.5)

0.75 (95%CI: 0.72-0.78; neutron weighting 2)

Photon scatter: Measured in phantom- previously published data

1.03 (95%CI:0.99-1.07; neutron weighting 5)

Total uncertainty in region of +/−33%

Yoon 2010 [53]

Out-of-field

Measured in phantom

Organ equivalent dose

PS

Relative risk compared to 6MV IMRT:

Stomach: 0.15

LP

Lung: 0.17

Thyroid: 0.10

Bladder: 0.40

Rectum: 0.51